Will I see a huge performance upgrade?

So I'm really debating on whether to upgrade my MacBook Unibody from late 2008, early 2009. It has the Core 2 Duo P7350 (2.0 GHz processor) and 4GBs of ram as well as a 1TB hard drive. Will upgrading to the current iMac or perhaps the newer iMac see a definite and noticeable performance boost?

I plan to do some video / photo editing, the occasional gaming and the more casual things as well. I want to do this since I pretty much carry my iPad all around instead now anyways unless I have major work but I plan to fix that with a Bluetooth keyboard case.

A new iMac is faster in everything that matters: RAM, CPU, hard drive, graphics. So I believe that the difference will be noticeable even to everyday use. I am basing this on my personal experience from the use of a Macbook (high end) and a Macbook Pro (mid range) that are only one year apart. The MBP is so much nicer to use, although on paper the differences seem fairly minimal.

But you will better notice the difference in video editing and gaming.

A new iMac is faster in everything that matters: RAM, CPU, hard drive, graphics. So I believe that the difference will be noticeable even to everyday use. I am basing this on my personal experience from the use of a Macbook (high end) and a Macbook Pro (mid range) that are only one year apart. The MBP is so much nicer to use, although on paper the differences seem fairly minimal.

But you will better notice the difference in video editing and gaming.

My old rule of thumb is that a speed improvement must be at least 3x to make a difference in how you work. This is because productivity and [perceived] improvements do not scale with speed. Some believe that the improvement scales as the logarithm of the speed. Others argue that it scales as the square root.

As computers get faster, the Law of Diminishing Returns becomes ever more significant. If a job that takes 10 minutes to complete on an old system takes only one minute on an new system, then the 10x speed improvement is a dramatic and useful improvement. If a task that takes 1 second on one system takes only 100 milliseconds on another, then the 10x speed improvement is not so useful.

None of the benchmarks show anything like a 10x or even a 3x improvement. The improvements are more like 30% or so. These will result in some tasks feeling smoother. For tasks like video conversion, rendering, and such like, the speed improvement may be useful.